Modern hearing instruments contain microphones. Although electret condenser microphones are typically used, MEMS-based microphones are gaining traction. Both types of microphone require that the transduction mechanism is loaded acoustically with small air volumes and also with an orifice that couples one or both of these air volumes to the outside medium. Consequently, each is susceptible to debris contamination, thereby rendering the microphone inoperable. In general, different forms of barriers have been used to protect the microphone, including meshes, screens, membranes, and coatings. Although those approaches may postpone failure from contamination, the microphones themselves will still fail if debris becomes attached onto their transduction mechanism (i.e., onto the membrane of an electret condenser or onto the silicon diaphragm of a MEMS) or if debris occludes an orifice of the acoustical loading. Thus the danger of this failure mechanism is always present.
There is a need, therefore, to integrate a robust microphone technology that would operate after being severely contaminated with debris.